1. Field of the Invention
The present invention relates to a Liquid Crystal Display ("LCD") and, more particularly, to an LCD having a light-shielding layer which is formed to overlap the wires of driver circuits with a minimum overlapping area.
2. Discussion of the Related Art
FIG. 1 shows a schematic view of a prior art LCD. An example is taken of an LCD where a light-shielding layer is formed on a color filter substrate.
Generally, a thin film transistor-LCD ("TFT-LCD") has a structure where a liquid crystal material 15 is interposed between a TFT array substrate (hereinafter referred to as "lower substrate") 10 and a color filter substrate (hereinafter referred to as "upper substrate") 20.
The lower substrate 10 has a centrally formed pixel element array portion 13, a gate driver circuit 12 and a data driver circuit 11, where the gate and data driver circuits 12 and 11 are disposed on the left and upper sides of the pixel element array portion 13, respectively. The gate driver circuit 12 drives the pixel elements of the pixel element array portion 13 and the data driver circuit 11 applies data signals to the pixel elements. Both of the driver circuits 12 and 11 are electrically connected to the pixel element array portion 13, respectively. The driver circuits 12 and 11 are also connected to an external circuit (not shown) to transfer signals of the external circuit to the pixel elements.
Although not shown in the figure, a plurality of gate and data lines are alternately arranged in the pixel array portion 13 to provide a plurality of pixel elements in a form. A transistor and a transparent pixel electrode electrically connected to driver circuits 12 and 11 are formed in each pixel element. In this respect, each driver circuit is connected to the external circuit so as to transfer the signals from the external circuit to the pixels.
The upper substrate has a plurality of color filters (not shown) having red, green and blue filters, respectively. Each color filter is formed corresponding to one of the pixel elements. A light-shielding layer 21 consisting of a metal, such as chrome, is disposed in a region between the color filters, that is, corresponding to a region of a metal pattern in the lower substrate, such as the data bus line, the gate bus line, and the thin-film transistor. A protective layer covers the surface of the color filter and the light-shielding layer. A common electrode for applying the electric field to the liquid crystals is formed on the protective layer. The figure shows the pattern of light-shielding layer 21 as a principal part for explaining the upper substrate.
The light-shielding layer 21 is so formed as to cover a region corresponding to the metal pattern, such as data bus line, the gate bus line, and the thin-film transistor of the lower substrate, thereby preventing light from leaking through regions other than the transparent pixel electrode. The light-shielding layer 21 has a pattern flat covers die whole area other tan the transparent pixel electrode of the lower substrate, so that it is formed in a matrix at a position corresponding to the pixel element array portion of the lower substrate.
FIG. 2 is a schematic view of the LCD taken by superposing area A onto area A' of FIG. 1, to explain how the wires of the driver circuit and the light-shielding layer overlap with each other.
The driver wire 11-1, 11-2, 11-3 and 11-4 are arranged at predetermined intervals in the driver circuit of the lower substrate. The light-shielding layer 21 is formed on the upper substrate to cover the whole area of the driver wires of the driver circuit.
In the prior art structure described above, the driver wires overlap with the light-shielding layer to form a capacitive coupling. The capacitive coupling refers to a phenomenon in which an insulating material is interposed between two electrodes mutually corresponding to each other and the signals of the one electrode affect those of the other. In the prior art, the driver signals applied to the driver wires of the driver circuit are distorted due to a capacitance formed by the driver wires and the light-shielding layer.
FIG. 3 is a partial equivalent circuit diagram of the driver wires and the light-shielding layer, where coupling capacitances are caused by the light-shielding layer of the upper substrate and the driver wires 11-1 and 11-2 of the driver circuit of the lower substrate.
In FIG. 3, C11, C12, C13, C14, . . . indicate the capacitances due to the light-shielding layer 21 and the first driver wire 11-1 while C21, C22, C23, C24, . . . indicate thc capacitances due to the light-shielding layer 21 and the second driver wire 11-2. Although not shown in the figure, the other bus lines and the light-shielding layer also form capacitances.
The coupling capacitances are insignificant in a small to medium-sized panel or a low resolution panel and minimally affect the LCD, but those arising in a large-sized, high resolution panel are large enough to distort or delay the signals applied to the driver wires. This results from an increase in the length and size of the driver wires with the larger panel. Consequently, it is desirable to form the driver wires having a conductive material with low resistance or to design the structure of the driver wires of the driver circuits to have a reduced capacitive coupling.
Accordingly, the present invention is directed to an liquid crystal display that substantially obviates one or more of the problems due to limitations and disadvantages of the prior art.
An object of the present invention is to prevent distortion of driver signals applied to driver wires by optimizing the pattern of a light-shielding layer to reduce capacitive coupling caused by an overlap of the driver wires and the light-shielding layer to a minimum.
Additional features and advantages of the invention will be set forth in the description which follows and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a liquid crystal display comprises a first substrate including a driver circuit having a plurality of driver wires and a pixel element array portion, a second substrate including a light-shielding layer and a color filter, and a liquid crystal material interposed between the first and second substrates, wherein the light-shielding layer is formed to overlap with the driver wires with a minimum area.
In another aspect of the present invention, a liquid crystal display comprises a first substrate including a driver circuit having a plurality of driver wires and a pixel element array; a second substrate including a light-shielding layer and a color filter, and a liquid crystal material between the first and second substrates, wherein the light-shielding layer overlaps the driver wires with a minimum area.
In another aspect of the present invention, a liquid crystal display comprises a first substrate including a driver circuit having a plurality of driver wires and a pixel element array; a second subs including a light-shielding layer and a color filter; and a liquid crystal material between the first and second substrates, wherein the light-shielding layer overlapping the driver wires includes strands of light-shielding material having a gap between at least two strands.
In another aspect of the present invention, a method of forming a liquid crystal display comprises forming a first substrate including a driver circuit having a plurality of driver wires and a pixel element array; forming a second substrate including a light-shielding layer and a color filter; and forming a liquid crystal material between the first and second substrates, wherein the light-shielding layer is formed to overlap the driver wire with a minimum area.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.